1. Field of the Invention
The present invention relates to an apparatus for processing a thin plate-shaped product in a gas atmosphere of high temperature and high pressure, and particular to a high-temperature high-pressure gas processing apparatus which enables loading and unloading of a workpiece to be processed within a short time in order to process a product in a short cycle. In recent years, the technique of crushing pores formed in via holes below an Al interconnecting film of a silicon semiconductor by using a high pressure gas at high temperature has attracted attention with demand for formation of fine interconnection. The apparatus of the present invention is particularly used for such processing.
2. Description of the Related Art
As a method of processing various materials under a gas atmosphere of high temperature and high pressure, hot isostatic pressing method (HIP method) is well known. This HIP method is industrially used for restoring pore defects in a metal casing, removing residual pores in a powder sintered product, sintering a powder material with a high density, and diffusion-bonding metals and ceramics. The HIP method can also be used for combination of the above-described purposes. For example, it has been proposed that after a film is formed on a surface of a metallic member by known evaporation, HIP processing is performed for eliminating void portions below the film and, at the same time, diffusion bonding the film to increase adhesive strength (Japanese Patent Laid-Open Nos. 54-33232 and 59-50177). This has been experimentally examined. The apparatus used in the HIP method is known as a hot isostatic pressing apparatus (HIP apparatus), and over 500 apparatus are being operated. The generally used HIP apparatus has a structure in which a resistance heating type electric furnace is incorporated into a cylindrical high-pressure vessel of a press frame type. A workpiece to be processed is unloaded downward or upward by removing an upper cover or a lower cover to open the high-pressure vessel to atmosphere. In cases wherein, after processing, the workpiece is unloaded from the HIP apparatus during the time the temperature of the workpiece is somewhat high so that the workpiece is effectively processed, oxidation by air is a problem. An apparatus is thus proposed in which a workpiece to be processed is handled in a vacuum or an inert gas without being exposed to air (Japanese Patent Publication No. 63-60308).
In these HIP apparatus, in the case of small workpieces to be processed, many workpieces are processed in one batch so as to decrease the cost of HIP processing. In the case of large workpieces to be processed, e.g., workpieces having a diameter of over 10 cm and a length of 1 m, a system is employed in which a workpiece at high temperature is unloaded from a high-pressure vessel, as described above, so as to decrease the cycle time and thus decrease cost. However, even in a short cycle, a cycle time of about 1 hour is required from loading to unloading.
It is, of course, possible to apply the HIP apparatus to removal of defects in the above-described Al interconnecting film on a silicon semiconductor (wafer). However, from the viewpoint of prevention of deterioration in the formed Al interconnecting film due to oxidation, it is particularly preferable that after the sputtering step of providing the Al interconnecting film, the wafer is transferred to an apparatus under vacuum for processing in a gas atmosphere of high temperature and high pressure so that the wafer is continuously processed. The use of the above apparatus disclosed in Japanese Patent Publication No. 63-60308 permits transfer in a vacuum or an inert gas atmosphere. However, since the sputtering step basically requires a time of the order of several minutes, a lot of some silicon wafers having Al interconnecting films formed thereon must be processed. Therefore, handling becomes complicated.
It has recently been proposed that removal of pores below the Al interconnecting films formed on silicon wafers is performed for each wafer in a gas atmosphere of high temperature and high pressure in linkage with the sputtering step (Japanese Patent Laid-Open No. 7-193063). In the above publication and another publication, Japanese Patent Laid-Open No. 7-502376, applied by the same applicant, an apparatus used for processing under high pressure is proposed.
This apparatus comprises a pressure vessel comprising a plurality of casing members which are closed by pressing by another means to form a high-pressure gas processing space, a system for supplying a high-pressure gas, and means for evacuating the pressure vessel.
The opening of the high-pressure vessel through which a wafer as a workpiece to be processed is moved in and out of the vessel is provided so as to cut crosswise a substantially disk-formed high-pressure gas space. In order to seal the high-pressure gas in this space, a method is employed in which the end of a taper face is pressed by the above pressing means.
In order to perform processing with a gas at high temperature and high pressure in synchronism with a film deposition process such as a sputtering process, and transfer a plate-shaped workpiece to be processed under a vacuum before and after the processing, it is effective from the viewpoint of reduction in the transfer time that the opening for unloading and loading the workpiece is formed so as to cut crosswise the high-pressure vessel, as in the above apparatus.
However, in order to perform this processing, it is important to maintain the opening portion in an airtight state during high-pressure processing, and it is necessary to continuously, stably and safely process a large number of workpieces to be processed.
In the above-described conventional technique, an actuator which is driven by a high-pressure gas at pressure in the same level as that used for processing is used as the pressing means for maintaining the opening in an airtight state, and the pressure-receiving area of the actuator is larger than that of a processing chamber so that, in a normal state, tightening force is always generated in the opening portion. In this apparatus, the opening portion is maintained in the airtight state even if a load acting on the actuator side is decreased due to a leakage of the gas on the actuator side through a valve. However, when the gas on the actuator side leaks at a high speed, if the valve has not a sufficient opening area, the gas does not flow at a sufficient flow rate, thereby causing a pressure difference. There is thus the possibility that the opening portion is opened.
In order to seal the opening portion, a method is proposed in which the edge portion of a circular member is pressed on an opposite member to maintain airtightness. However, this method has a problem in that the selection of the circular member is difficult, and the use of a metal, which is a material having heat resistance and low out gas, causes plastic deformation of the edge portion due to tightening at each processing cycle, and work hardening which makes the edge portion impossible to resist repeated use.